Drive motor options

[RogueTwoRobots]

I think 720 uses the 16:1s with 775 motors, this will give you a rough idea of speed:



EDIT: Forgot to add, that's with 98mm wheels.

[Liftoff]

Just landed a couple of min ago, and having nothing to do on a 3hr flight I got myself through a lot of immaginative thinking regarding gearboxes etc...and got this idea of a compact planetary gearbox which could stay inside a wheel. ..have to think about this some more, put it into writing and make some sketches before I forget.
Will explain myself better when I get a clearer idea myself of what I'm talking about!

I think 720 uses the 16:1s with 775 motors, this will give you a rough idea of speed

Wow! thats seriously fast!...hmm...to be honest I think I like the idea of something that goes that fast!

Ellis, the wheels are 64mm in dia but with the track on, the effective dia becomes 74mm so that's close to your estimate. Regarding the added stresses on the tracks on skidding sideways, you're probably right...but they ain't going nowhere. The way they're mounted now its impossible to throw a track off...so might as well give it a try! Honestly I doubt it will side slip much with tracks, they're quite grippy!

The sabretooth, well if statistically it should be able to drive both motors I'll go ahead and use it, useless having it there to gather on dust! It's more honourable for it to die in battle!

[daveimi]

"...got this idea of a compact planetary gearbox which could stay inside a wheel..."

Tanto uses this setup

[Eventorizon]

I think 720 uses the 16:1s with 775 motors, this will give you a rough idea of speed:

EDIT: Forgot to add, that's with 98mm wheels.

Wow! thats seriously fast!...hmm...to be honest I think I like the idea of something that goes that fast!

Yes, that is correct. Dave says that it wheels spins like crazy but it still gets good acceleration. Conker 3 is running the same set up but with 4x 73mm banebots wheels. That obviously wont have such a high top speed but it should accelerate like crazy and have almost no wheel spin.

[maddox10]

and got this idea of a compact planetary gearbox which could stay inside a wheel. ..have to think about this some more, put it into writing and make some sketches before I forget.
Will explain myself better when I get a clearer idea myself of what I'm talking about!

Skyfall uses that idea, as well Firestarter (Dutch Feather using Astroflight motors). And that's the current feathers.

Project One and Two used the same idea a decade ago.

[Liftoff]

Skyfall uses that idea, as well Firestarter (Dutch Feather using Astroflight motors). And that's the current feathers.

Project One and Two used the same idea a decade ago.

Good, saves me the thinking! Any links to the gearboxes?

Another thing, was discussing the options for the motors with my brother (he's more knowledgeable on electrics than I am) and mentioned brushless motors, are they suitable for combat robots? The main issue I see is gearing them down to a reasonable speed, but otherwise they seem to be smaller lighter and more powerful to their brushed counterparts....
I know I'm asking too much, but while I'm at it I prefer to evaluate all options to make an informed decision and save myself from ordering needless or wrong parts!

[Ellis]

Brushless motors go plenty low enough in rpm. Lower than equivalent diameter motors by far in some cases; the 775 can motor that Banebots use do 20,000rpm at nominal v.

The motors themselves are suitable, the issue is with speed control. It's hard to find a brushless speed controller that will not only do reverse, but not have a delay between fwd/rev. Some RC-car speedos do this, but they're generally lowish voltages (3-4s). Also, brushless motors can't just have their polarity switched to bang into reverse like brushed. They have to come to a complete stop before being able to change direction, further reducing drive responsiveness. Not many have experimented with brushless drive as a result, though once the speed controllers exist, the potential is huge. They are massively powerful.

This Australian build thread shows a machine with brushless drive, but there isn't much detail: http://robowars.org/forum/viewtopic....=asc&start=615

[Max]

The other thing I thought of was using the newish brushless dewalt cordless drills- I imagine this could provide a good brushless motor with the appropriate gearing already made up so it can give the same speed output as a normal drill.
I dare say these new drills are expensive and parts will probably have to be machined to hold the motor and gearbox together but I guess it's an option if you can find a speed controller.

[maddox10]

Good, saves me the thinking! Any links to the gearboxes?

Firestarter
http://www.bugs.nl/media/album/view....J0ZXIvOS5qcGc=

Skyfall with explanation
http://i172.photobucket.com/albums/w...ps104ee1f4.jpg

[Liftoff]

I take it those are custom built boxes Mario, right? They look well suited for my use if they can fit inside a 54mm dia 40mm wide wheel.

Better stick to brushed motors then, rather than getting into problems controlling a brushless setup. That said I think I've seen a local team using a brushless setup on their robot...not sure tho as I only saw a photo of the underside and what looked like two brushless motors. Will try to find the photo and post it here, maybe someone can identify the components.